ABSTRACT:
Throughout history greening of outside walls and roofs of buildings has been the case. Reasons for
doing so were the increase of insulation (keep cool in summer and keep cold out in winter), improved
aesthetics, improved indoor and outdoor climate, catching of NOx and Particulate Matter (PMx), as
well as increasing ecological values by creating habitats for birds and insects.
When we look at the facades or outside walls of buildings, green systems will show ecosystem
characteristics, it will function as a habitat, will show structure, material and energy flows. But it will
also provide ecological services like breeding and resting habitat for birds which may be enjoyed by
humans, it will give extra insulation (reduced energy consumption in winter as well as summer),
interception of rainwater, reducing air pollution (uptake of NOx and particulate matter PMx), reduction
of noise level as well as change of perception of noise and increasing aesthetic value.
In recent years there has been much interest in the health implications of fine particles in the
atmosphere. Particulate matter having an aerodynamic diameter of less than 10 µm (PM10) has become
the standard measure of this form of air pollution. Atmospheric particles, especially those with an
aerodynamic diameter of <10µm (the smaller particles of the PM2,5 size range are considered as the
most damaging to health, since they can more easily penetrate the respiratory tract.), pose a long-term
threat to the human health, in particular to human respiratory functions.
In this SUA colloquium I will present some research plans, the possibilities of greening facades and
some results from my experimental data.
Introduction
In the Netherlands all kinds of measures are carried out that must ensure that the environment
is less charged. On one hand these measures are a consequence of (legal) obligations, which
result from international conventions as for example the Kyoto protocol [1]. Other measures
are the consequence of international political agreements [2]. Especially the rules concerning
air polluting substances has been considerably tightened up the last years. According to the
Kyoto protocol the Netherlands must reduce the emission of greenhouse gases in the period
2008 up to 2012 with an average of 6 percent compared to the base year [3]. Thereby a part of
this reduction can/may be realised abroad.
The emission in the base year is among other things determined on 214,3 billion kg CO2
equivalents. In 2004, the CO2 emission was 181 billion kg and in 2006 there was a reduction
to 172 billion kg CO2.
Air pollution is the phenomenon where our surrounding air (atmosphere) is polluted by
substances which do not belong there. It concerns thus the quality of air. The atmosphere
exists from approximately 80% nitrogen, 20% oxygen and very small quantities of other gases
under which carbon dioxide and water vapour. Combustion processes in the industry, traffic
and households pollute the air with among other things Carbon dioxide (CO2), Carbon
monoxide (CO), Nitrogen oxides (NOx) and Particulate Matter (PMx). Air pollution is a crossborder problem: the air polluting substances in the Netherlands come for 60 up to 80 percent
[4] from foreign countries. Oppositely a large part of the expelled substances in the
Netherlands arrives however abroad.
Particulate matter for example is one of those air polluting substance. Atmospheric particles,
especially those with an aerodynamic diameter of <10µm (PM10), pose a long-term threat to
the human health, in particular to human respiratory functions. In the Netherlands the
National Institute for Public Health and the Environment (RIVM) calculated that about 18.000
thousand people die prematurely by the causes of particulate matter.
Particles are removed from the atmosphere by dry, wet or occult deposition (Fowler et al.,
2001). The dry deposition is the removal of pollutants by gravitational settling, impaction and
interception. Vegetation is an efficient scavenger of particulate matter. Particle collection is
due to the interaction of particles with vegetation surface (leaves, trunks and twigs).
Vegetation has a large collecting surface area and also promotes vertical transport by
enhancing turbulence, so there is a greater opportunity for particles to be collected on the
vegetation surface. Applying living walls and with that a great sink for air polluting
substances leads to a contribution of the air and ecological quality.
Improving the air quality is examined on a lot of fronts. The possible application of vegetation
within and around urban areas for a positive contribution to the air quality is one of them.
Also one can think of catalytic processes which will reduce the quantity of detrimental
substances. In the dissertation there will be more examined if the use of green facades can
give a positive contribution to the air quality. With this, also a visualisation will be made on
how large this positive contribution can be on the air quality in the urban area.
1.1 Aim of the research
The aim of the project obtains to get more insight in the (potential) contribution of
improvement of the air quality by (greening) building facades. Also the ecological aspect of
green facades must be examined in the research. As objective(s) will be used:
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To obtain and get insight in how the skin of a facade can contributes to an
improvement of the air quality.
To obtain and get insight in how the skin of a facade can contribute to an increase of
the ecological quality.
To develop a model on the basis of the obtained insight(s) and data that can be used on
façade, building, district and urban area level. The model can be used for calculating
the impact of several forms of vegetation to enlarge the ecological quality and
reducing air pollution substances.
1.2 Approach of the research
With the given objective(s) the approach of the research is not determined yet. The research
approach will be briefly commented in this paragraph. The research will show an explorative
and hypothesis chapped character, with in the end, as aim to get a design tool or assessment
instrument for designers and architects.
The design tool or assessment instrument will arise on the basis of the exploring research. The
gaps and necessarily required additional data will be completed by means of experiments. In
the study will be examined what the possible impact is on the concentration of air polluting
substances by applying green facades. By means of a literature study will be examined what
the main sources are for air pollution. Also the different mechanisms behind converting air
pollution will be explained. The classification of the term façade and surroundings will be
specified more closely.
1.3 Research questions
Using the given beginning for a research approach the research questions can be distilled from
the objective(s). The research questions will give more form to the research. The structure of
the research will arise by the drawing up of a time schedule and the gained results in a period
corresponding to the time schedule.
Main question:
How can a green façade contribute to existing (conversion) processes to reduce carbon
dioxide, nitrogen oxides and particulate matter with thereby as aim realising an improvement
of the air and ecological quality?
The main question involves an exploring study between the relations into facades and air
quality. With this the meaning of using a (multipurpose) facade must be examined on the
improvement of air quality. The next sub questions are therefore relevant:
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What is the (main) source of air polluting substances such as carbon dioxide nitrogen
oxides and particulate matter?
What is the aim of reducing the concentration of these air polluting substances?
How is it possible to reduce or fix the concentration of air polluting substances?
Lead the ecological use of vegetation on or against a façade to an improvement on
the air and ecological quality?
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On which way is it possible to let vegetation be a part of the building?
Background questions:
 Has the use of vegetation influence on the durability of a façade?
 Which possible damage mechanisms have to be taken into account?
 Leads the use of (multipurpose) facades to the desired reduction of air pollution
substances and to an increase of the ecological quality?
 Which vegetation methods are the most suitable for application on/against a façade
with regard to air purifying and increasing of the ecological quality?
 What is the contribution of a green façade to the total reduction of air purifying
substances?
 What is the influence of a green façade on the air flows and turbulence for scavenging
particulate matter?
 What is the effect of vegetation on the total emission of air purifying substances?
1.4 Research objectives
The research will be set up from central points. The central points will gave further form to
the research. Additionally, it is possible to couple an associated time plan to the central points,
the gained results and reached mile stones. The concerning central points of the research will
include:
1. Make a state or the art report containing the most relevant aspects.
- Effect vegetation on distribution, capturing and converting air pollution
leading to a description of the ecological environment of the (green) skin of a
façade and environment.
2. Overview of technical instruments (assessment tools as for example GreenCalc+ and
Eco indicator 99) for the application of the life cycle analysis methodology.
3. Analysis of existing and to develop (green) skin designs that can give a contribution to
the improvement of the air and ecological quality and the perception of the
environment.
4. The choice of a number detailed skin designs (in situations as for example a wind
tunnel or air flow models).
5. The development of a model in aid of quantitative based assessments of the
contribution to an increase of the air and ecological quality and reduction of the
impact of air pollution.
Beside the central points the research will exist of a literature study which will provide the
required knowledge concerning air quality and emission resources. Additionally, attention
will be given on the positive impact of biochemical deterioration. The total work will be
ended with a chapter discussion, recommendations and conclusion.